Do Flashers Kill Battery?

Flashers or hazard lights are crucial for safety, but leaving them “on” for too long will be the culprit for draining your car’s battery. Many drivers know that hazard lights should not be used when parking in a garage or dark area to avoid confusing other motorists with their signals. However, it is easy to forget this rule of thumb and leave the hazard lights on while driving on an isolated desert road or a snowstorm. As a result, it would discharge or kill your battery quickly. Check out this blog post to know the reasons behind it and understand how hazard lights or flashers in your vehicle work.

How long can hazard lights stay on before the battery dies?

Often people don’t realize that leaving hazard lights “on” can dramatically lower their car’s battery life and reduce the vehicle life. Some hazard lights drain a car’s battery in minutes, while others can last hours. Even though it’s tempting to use your hazard lights when you feel stranded, the battery will die in a few hours (about 4 to 5 hours) if they are kept on.

If you know how long before hazard lights drain battery, you can avoid getting stranded on the side of the road.

Should I leave my hazards on?

Leaving hazard lights “on” is a personal choice and depends on your kind of hazard lights. If your flashers are turnable, there is no need to worry about battery life as they will only work when turned back on. Hazard lights automatically shut off on some older model cars (the early 2000s) after turning them on for 20 minutes. If this is the case, it is best to shut them off after you are done using them.

Remember that when hazard lights are used, the power they draw is pulled from your vehicle’s main electrical system, including your engine and all of its components. Leaving hazard lights on for too long will reduce the life of your car‘s battery.

Do hazards stay on when a car is off?

If the hazard lights are left on after the car is turned off, this might drain your battery. Thus, it’s best to turn them off when you’re not in your vehicle with the engine running. Think of it as a safety feature for fellow motorists. An extended flash can blind other drivers or pedestrians in your vicinity.

It’s not just about draining your battery. If the car dies out completely, leaving the hazard lights “on” for too long might leave you stranded. When the battery on your car is dead, it will no longer provide enough current for the hazard lights to work. The switch can be used as a reminder that you need another set of headlights or taillights when driving during dimming hours.

How long can emergency lights be on?

Some sources say you can leave your hazard lights on for at least 15 minutes before draining the battery for older cars without electronic or digital gauges. However, modern cars have computers, and most will shut off when they get too hot. If you leave your hazard lights on too long, the computer in the vehicle could burn out and cost hundreds of dollars to replace.


It’s essential to remember that hazard lights are intended to use in an emergency. However, a few things may happen if you decide to leave them on for too long. These include draining your car battery quickly, damaging your vehicle itself, and affecting your car’s components such as the air conditioner and defroster when left running in extreme heat or cold temperatures. Therefore, if you want to save your battery, start conserving energy in other ways. Don’t leave interior lights on overnight; turn off everything unnecessary when driving, such as the radio, heater, air conditioning, etc.

About the author, Phil Borges

Phil Borges is a battery aficionado. He's written extensively about batteries, and he loves nothing more than discussing the latest innovations in the industry. He has a deep understanding of how batteries work, and he's always on the lookout for new ways to improve their performance.